Temperature responsive electric switch



July 7, 1970 v P. MERRILL 3,519,972

TEMPERATURE RESPONSIVE ELECTRIC SWITCH Filed March 18, 1969 2 Sheets-Sheet 1 IO 22 52 5O 34 I 62 24 54; 46 f 30 44 6O v v 42 '8 v FIG.3

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I82 I; r 20 w 42 INVENTOR F |G.6 PHILLIP EDWARD MER'RILL BY M WW HIS ATTORNEYS y 7, 1970 P. MERRILL 3,519,972

TEMPERATURE RESPONSIVE ELECTRIC SWITCH Filed March 18, 1969 2 Sheets-Sheet 2 u/y Lggw \p I02 92 T o 44 O4 1023 84 FIG] INVENTOR. PHILLIP EDWARD MERRILL HIS ATTORNEYS United States Patent 01 fice 3,519,972 Patented July 7, 1970 3,519,972 TEMPERATURE RESPONSIVE ELECTRIC SWITCH Phillip Edward Merrill, Kettering, Ohio, assignor to Micro Devices Corp., Dayton, Ohio, a corporation of Ohio Filed Mar. 18, 1969, Ser. No. 808,247 Int. Cl. H01h 37/72, 37/76 U.S. Cl. 337--407 33 Claims ABSTRACT OF THE DISCLOSURE A switch construction has a conductive casing with an integral closure at one end and an electrically nonconductive closure at the other end. One conductor contacts the casing and a second conductor extends into the casing through the non-conductive closure. The non-conductive closure is a rigid insulating plug surrounding said second conductor having a large main body engaging the inside of the casing, with two identical smaller diameter inward and outward plug extensions. Either plug extension is inserted into the casing and the other extension extends out of the casing. The other switch parts are first inserted into the casing before insertion of the plug in the casing. A sealing compound is then applied to the plug, to the adjacent end of the casing, and to the second conductor, which extend out of the plug. Another embodiment has the cylindrical main plug body and the outward plug extension. The plug has an inward conductive pin at the other end that engages a second conductor end head in a cavity in said main body.

SUMMARY OF THE INVENTION This application relates to a switch construction having a cylindrical tubular electrically and thermally conductive casing having an integral closure at one end and having an electrically non-conductive closure at the other end. A first conductor conductively contacts the casing and a second conductor extends into the casing through the non-conductive closure. The non-conductive closure includes a rigid insulating plug surrounding said second conductor and having a large diameter cylindrical main body engaging the inside surface of the conductive casing, said plug having two identical smaller diameter inward and outward plug extensions. The plug is not required to be oriented for insertion into the casing and either plug extension may be inserted first into the casing and the other extension may extend out of the casing. The other switch parts are first inserted into the casing in a proper manner and then the said insulating plug is inserted in the casing and a sealing compound is applied to the outward extension of the plug, to the adjacent end of the casing, and to the second conductor, which extends out of the plug. The switch parts are so arranged that the electrical interruption capacity of the switch is greatly increased. Also, the cost of assembly is greatly reduced, while the conductivity of the switch is greatly increased, and the current resistance is greatly decreased.

In another embodiment of this invention, the insulating plug has the cylindrical main body and the outward plug extension. However, the plug has a movable conductive pin at the other end that engages a second conductor end head in a cavity in said main body of the plug to increase the conductivity in one position and to increase the interruption capacity in the other position.

Other advantages and features are apparent from this description, the accompanying drawings, and the appended claimed subject matter, in which:

FIG. 1 is a longitudinal cross section of one embodiment of the invention.

FIG. 2 is a cross section of the insulative plug.

FIG. 3 is an elevation of the relatively weak spring.

FIG. 4 is a cross section of the electrically conductive slidable member.

FIG. 5 is a longitudinal cross section of another embodiment of the invention.

FIG. 6 is an elevation of the completed switch of all of the embodiments of this invention, the switch being drawn substantially on the same scale and size as the actual switch construction on the application drawing.

FIG. 7 is a longitudinal cross section of another embodiment of this invention.

FIG. 8 is a view of certain parts of FIG. 7 with the pin having been moved following collapse of the pellet.

In FIGS. 14, a switch or switch construction 10 may comprise a cylindrical, tubular, electrically and thermally conductive casing 12 having closures 14 and 16 at each end of the casing 12. The closure 16 may be an electri cally non-conductive closure.

A first conductor 18 conductively contacts the casing 12, such as at the integral closure 14. A second conduc tor 20 extends into the casing 12 through the electrically non-conductive closure 16. A normally solid fusable pellet 22 is spring-biased to exert outward pressure against one of the closures, such as the closure 14.

An electrically conductive member 24 is slidably mounted within the casing 12. The member 24 has a slidable, resilient peripheral conductive engagement with the conductive casing 12, such as by the outwardly resilient integral teeth 26, which outwardly press against the inner surface of the conductive casing 12. The member 24 also has a conductive central portion 28 in electrical flow condition with said second electrical conductor 20 in one position of the member 24 and out of electrical flow condition with said second electrical conductor in another position of said member 24.

A compression spring construction outside of the pellet 22 is held under compression between the member 24 and the casing 12 to change the electric flow condition between the casing and the electrical conductor 20 upon collapse of the pellet 22, such as by leftward movement of the conductive member 24 away from electrical contact with the conductor 20.

The non-conductive closure or plug 16 may have a central opening 30 surrounding the second conductor 20, and the plug 16 may be secured in the conductive casing 12 at the right casing end. The insulating plug 16 may have a large diameter, cylindrical, main body 32 engaging the inside surface 34 of said conductive casing 12.

The plug 16 may have two identical, smaller diameter, inward and outward plug extensions 36 and 38, with said outward plug extension 38 extending out of one end of the conductive casing 12 and with said inward plug extension 36 extending into the conductive casing and engaging a conductor arresting means, such as conductor head means 40, at the inner end of the second conductor 20.

A sealing compound 42 surrounds a portion of the outward plug extension 38, a portion of the second conductor adjacent the outward plug extension 38, and 1s sealed against the right end of the casing 12, such as at the inward flange 44. Such inward flange 44 holds the plug main body 32 and the outward plug extenslon from outward movement.

The identical plug extensions 36 and 38 have identical gradually decreasing surface diameters, as shown in FIGS. 1, 2 and 5, and such extensions also have flat transverse end surfaces 46 and 48, with the flat surface 46 engaging and holding the head means 40 to prevent outward movement of the second conductor 20 out of the casing 12 and plug 16.

The casing 12 has a thinner wall portion 34 at sald one or right end of the conductive casing 12, with inward casing flanges 44 and at each end of the thinner p rtion 34. The thinner wall portion 34 thus holds the mam body 32 of the plug 16 and the inward casing flanges 44 and 50 hold the plug extensions 36 and 38 from longitudinal movement.

The compression spring construction may include a relatively strong compression spring 52 between the pellet 22 and the electrically conductive member 24. Such compression spring construction also may have a relatively weak compression spring 54 between the plug 16 and the electrically conductive member 24. As long as the pellet 22 does not collapse, the strong spring 52 holds the slidable conductive member 24 against the head 40 of the conductor 20, so that there is an electrical flow condition between the second conductor 20 and the easing 12 and the first conductor 18. However, when the pellet 22 collapses, the material of such pellet 22 substantially instantaneously becomes fluid and flows around a disc means 56, and allows the strong spring 52 to expand toward closure 14 so that its spring load becomes less than the spring load of the relatively weak spring 54. This permits such weak spring 54 to move the conductive member 24 away from the conductor head 40 and thus the conductive member 24 becomes out of electrical flow condition with respect to the second electrical conductor 20 and thus breaks the electrical flow condition between the conductors 20 and 18 to stop the flow of current through them.

The disc means 56 is a spring load distributing disc means, is of less diameter than the adjacent inner surface of casing 12, and is adjacent one end of the strong spring 52. The strong spring 52 may have another spring load distributing disc means 58 adjacent its other spring end. The disc means 58 may be of less diameter than the adjacent inner surface of casing 12. In this manner, the disc means 56 and 58 distribute the spring load of spring 52 against the pellet 22 and against the central part 28 of slidable member 24. The discs 56 and 58 may be flat sided metal or conductive discs, and thus effectively distribute the spring loads.

The first electrical conductor 18 may be secured to the integral conductive end wall closure 14 by the flange means 60 and 62. The pellet 22 may be adjacent or near the integral conductive end wall 14, as illustrated.

The disc means 58 is adjacent one of the spring ends of the weak spring 54, but on the left side 28 of slidable member 24, and distributes the spring load of such weak spring 54 by backing up the central portion 28 of the slidable member 24 and to prevent bulging of such central portion 28, as may be seen in FIG. 1.

In the operation of the embodiment of FIGS. 14, opposite power lines may be connected respectively to conductors 18 and 20, with conductivity between such conductors. The parts of the switch 10 remain in conductive condition and in the positions illustrated in FIG. 1 as long as the casing 12 remains at a temperature below the collapse temperature of the pellet 22. However, when the environment temperature heats the casing 12 adjacent the pellet 22 substantially to such collapse temperatures, the

4 pellet 22 collapses and becomes fluid or otherwise movable past disc 56. This permits the disc 56 and the left end of strong spring 52 to move leftwardly enough to reduce its spring load below that of weak spring 54. This permits the spring 54 to move the movable member 24 leftwardly away from head 40 and thus break the conductivity condition between the conductors 18 and 20.

FIG. 5 shows another embodiment somewhat similar to the embodiment of FIG. 1. However, the disc means 64 of FIG. 5 is placed adjacent the conductor head means 66 of the second conductor 68. Otherwise, all of the parts of FIG. 5 may be identical with the corresponding parts of FIG. 1 and therefore such parts are not again cornpletely described in connection with FIG. 5.

The head 66, in FIG. 5, has a substantially flat portion 70, with a rounded edge 72. This permits the flat portion 70 to provide a relatively large surface and good electrical conductivity between the second conductor 68, disc means 64, slidable member 24 and the casing 12. At the same time, the disc 64 provides substantially the same load distributing characteristics as the disc 58 in FIG. 1 for both of the springs 52 and 54.

The head 40 of FIG. 1 may be somewhat, or almost, continuously rounded to provide a good conductive contact between the head 40 and the flat portion 28 of slidable conductive member 24. The head 68 of FIG. 5 is made of good conductive metal and has an extensive flat surface contact at the flat surface 70 with the flat sided good conductive disc means 64. This provides a very good conductive contact between the head 68 and the slidable conductive member 24 which is better than the corresponding parts in FIG. 1. The small rounded edges 72 of head 66 are sufficient to prevent arcing when the head 68 and disc 64 are separated. When the flat surfaces of head 54 and disc 64 are separated, such fiat surfaces therefore have greater interruption capacity because of such flat surfaces and small rounded edges than in corresponding parts of FIG. 1.

Therefore, the embodiment of FIG. 5 has a better electrical conductivity and also has a greater interruption capacity of resistive loads than the embodiment of FIG. 1.

All of the other parts of FIG. 5 may be substantially the same instructure and function as the obviously corresponding parts of FIG. 1 and it is therefore believed unnecessary to repeat their description.

In the embodiment of FIGS. 7 and 8, many of the parts may be identical with those previously described in connection with FIGS. 1 and 5. However, the insulative plug 74 of FIGS. 7 and 8 has a central opening 76 surrounding the second conductor 78. The plug 74 may be located and secured in the conductive casing 12 and may have a large diameter cylindrical main body 80 engaging the inside surface 34 of the conductive casing 12. The plug 74 may have a smaller diameter outward plug extension 82 out of the one or right end of the conductive casing 12.

The plug 74 may have a relatively large plug cavity 84 with an opening 86 extending toward the interior of the conductive casing 12. The cavity 84 may also have a cavity bottom 88 adjacent the outward plug extension 82.

The second conductor 78 has an arresting conductor head means 90 which may be substantially the same as heads 40 and/or 66, but somewhat larger. Such head means 90 may engage the cavity bottom 88 to hold the second conductor 78 from moving outwardly. Such second conductor 78 extends out of the central opening 76 of said smaller diameter outward extension 82.

A relatively thick conductive pin 92 has one end 94 engaging the head means 90. The pin 92 extends out of the plug cavity 84 and has a pin head S96 engaging the conductive member 98. The pin head 94 may have a substantially flat end surface with small rounded edges.

The pin 92 and the slidable conductive member 98 are simultaneously movable away from the electrical fiow condition of FIG. 7 so that the second conductor 78, in FIG. 8, is out of electrical flow condition with the pin 92 by creation of the large insulative air space 100' between the head 90 and the end 94 of the pin 92.

Other parts of the embodiment of FIGS. 7 and 8 are substantially the same as has been described in connection with FIGS. 1 and 5, and only the parts that have been changed are further described now.

The sealing compound 102 of FIGS 7 and 8 covers the flange 44, the extension 82 and a portion of the second conductor 78 substantially in the same manner as previously described. The flanges 44 and 50 of FIGS. 7 and 8 hold the main body 80 of the plug 74 substantially in the same manner as in FIGS. 1 and 5.

The plug outward extension 82 has a transverse end surface substantially the same as surface 48 of FIG. 1.

The compression spring construction of FIGS. 7 and 8 includes the relatively strong spring 104 and the relatively weak spring 106 which engages the flat end 108 of the plug 74 and the outwardly extending disc-like flange of pin head 96 of the pin 92. The pin head 96 acts as a weak spring load distributing disc means to distribute the spring load of the spring 106 against the slidable conductive member 98. Likewise, the pin head 96 acts as a backing up spring load distributing means for the strong spring 104.

Since the other parts of the switch construction shown in FIGS. 7 and 8 are substantially the same as in FIGS. 1 and/or 5, it is believed unnecessary further to describe such parts.

The space or cavity 100 of FIG. 8 establishes a large insulative barrier between the second conductor 78 and the first conductor 110 that provides higher interruption capacity of electrical loads in the embodiment of FIGS. 7 and 8 than is accomplished in a corresponding construction such as is shown in FIGS. 1 and 5. The thick pin 92 and large disc-like pin head 96 provide better conductivity than corresponding constructions of FIGS. 1 and 5.

The various parts of the switch may be made of materials now well known to be suitable for this type of construction.

For example, the electrical conductors 18, 20, 68, 78, 110 may be made of copper and may be silver plated. The casing 12 may be made of brass. The compound 42 may be of high temperature resistant epoxy resin, or other suitable high temperature resistant non-electrically conductive material. The pellet 22 may be of any suitable type, now well known in the art, and which may now be purchased on the market merely by specifying the desired collapsing temperature, size, etc. These pellets have a rigid body which is not collapsible when subjected to any pressures of the springs used in the. switch as long as the ambient temperature is below the selected collapsing temperature. When the pellet reaches the selected collapsing temperature, within narrow limits of one or two percent, for example, the pellet melts or otherwise disintegrates so that the spring action can operate as pre viously described and also almost instantaneously.

A great advantage is obtained in the embodiment of FIGS. 1 and because the plug 32 is insertable in the casing 12 with either extension first without a selecting operation to provide a selected end to be first inserted. The same is true of the weak spring 54 of FIGS. 1 and 5 which is made to have a constant diameter with both ends identical so that either end may be inserted first without an end selecting operation.

A great advantage is obtained in the embodiments of FIGS. 7 and 8 because of the improved conductive construction and because of the large insulative electrical barrier produced by the large space at 100 which breaks the conductive flow condition between the electrical line conductors 78 and 110.

The outward extensions 38 and 82 of the plugs 16 and 74 also have a large electrical barrier along the insulative compound 42.

Many of the parts are very small in a switch of this size. Where such parts have conductive contact surfaces such contact surfaces may be silver coated, or such parts may have their entire surfaces silver coated, if desired, at no substantial increase in cost because of their small size.

The operation of the embodiment of FIG. 1 has been previously described, and it is believed that the operations of the embodiments of FIGS. 5 and 7-8 are now obvious in view of the foregoing description of the new structures of such figures.

What is claimed is:

1. A switch comprising: a cylindrical tubular electrically and thermally conductive casing having a closure at each end of said casing; one of said closures being electrically non-conductive; a first conductor conductively contacting said casing; a second conductor extending into said casing through said electrically non-conductive closure; a normally solid fusible pellet spring biased to exert outward pressure against one of said closures; an electrically conductive member slidably mounted within said casing, said member having a resilient peripheral conductive engagement with said conductive casing, and having a conductive central portion in electrical flow condition with said second electrical conductor in one position and out of electrical flow condition with said second electrical conductor in another position; a compression spring construction outside said pellet held under compression between said member and said casing to change the electric flow condition between said casing and said electrical conductor upon collapse of said pellet; said non-conductive closure including a rigid insulating plug having a plug central opening surrounding said second conductor, said plug being located and secured in said conductive casing and having a large diameter cylindrical main body engaging the inside surface of said conductive casing, said plug having two identical smaller diameter inward and outward plug extensions, with said outward plug extension extending out of one end of said conductive casing and with said inward plug extension extending into said conductive casing and engaging a conductor arresting means at the inner end of said second conductor.

2. A switch construction according to claim 1 in which a sealing compound surrounds a portion of said outward plug extension.

3. A switch according to claim 2 in which said sealing compound surrounds a portion of said second conductor adjacent said outward plug extension.

4. A switch according to claim 3 in which said sealing compound is sealed against said one end of said casing.

5. A switch according to claim 1 in which said one end of said casing has a casing inward flange to hold said outward plug extension.

6. A switch according to claim 5 in which said sealing compound seals against said inward flange.

7. A switch according to claim 1 in which said plug extensions have identical gradually decreasing diameters.

8. A switch according to claim 7 in which said plug extensions have flat transverse end surfaces.

9. A switch according to claim 1 in which said casing has a thinner wall portion at said one end of said conductive casing with inward casing flanges at each end of said thinner wall portion, said thinner wall portion holding said main body of said plug and said inward casing flanges holding portions of said plug extensions.

10'. A switch according to claim 1 with said compression spring construction including a relatively strong compression springbetween said pellet and said electrically conductive member and with a relatively weak compression spring between said plug and said electrically conductive member.

11. A switch according to claim 10 with said strong compression spring having spring load distributing disc means adjacent one end of its spring ends.

12. A switch according to claim 10 with said strong compression spring having a spring load distributing disc means adjacent one of its spring ends and having another spring load distributing disc means adjacent another of its spring ends.

13. A switch according to claim 10 with said conductive casing having an integral conductive end wall closure at the other end of said conductive casing, and with said first conductor connected to said conductive end wall closure.

14. A switch according to claim 10 with said weak spring having both ends of identical diameter.

15. A switch according to claim 10 with said weak compression spring having spring load distributing disc means adjacent one of its spring ends.

16. A switch construction according to claim 1 with said conductor arresting means being a conductor enlarged end head means engaging said inward plug extension.

17. A switch comprising: a cylindrical tubular electrically and thermally conductive casing having a closure at each end of said casing; one of said closures being electrically non-conductive; a first conductor conductively contacting said casing; a second conductor extending into said casing through said electrically non-conductive closure; a normally solid fusible pellet spring biased to exert outward pressure against one of said closures; an electrically conductive member slidably mounted within said casing, said member having a resilient peripheral conductive engagement with said conductive casing, and having a conductive central portion in electrical flow condition with said second electrical conductor in one position and out of electrical flow condition with said second electrical conductor in another position; and a compression spring construction outside said pellet held under compression between said member and said casing to change the electric flow condition between said casing and said electrical conductor upon collapse of said pellet; said non-conductive closure including a rigid insulating plug having a plug central opening surrounding said second conductor, said plug being located and secured in said conductive casing and having a large diameter cylindrical main body engaging the inside surface of said conductive casing, said plug having a smaller diameter outward plug extension extending out of one end of said conductive casing, said plug having a relatively large plug cavity in said main body with an opening extending toward the interior of said conductive casing and with a cavity bottom adjacent said outward plug extension, said second conductor having an arresting conductor head means engaging said cavity bottom to hold said second conductor from moving outwardly, and said second conductor extending out said central opening and out of said smaller diameter outward plug extension, and a conductive pin having one end engaging said conductor head means, said pin extending out of said plug cavity and having a pin head engaging said conductive member, said pin and said conductive member being simultaneously movable away from electrical flow condition with said conductor head.

18. A switch according to claim 17 ln which a sealing compound surrounds a portion of said outward extension.

19. A switch according to claim 18 in which said sealing compound surrounds a portion of said second conductor adjacent said outward plug extension.

20. A switch according to claim 19 in which said sealing compound is sealed against said one end of said casing.

21. A switch according to claim 17 in which said one end of said casing has a casing inward flange to hold said outward plug extension.

22. A switch according to claim 21 in which said sealing compound seals against said inward flange.

23. A switch according to claim 17 in which said plug outward extension has a flat transverse end surface.

24. A switch according to claim 17 in which said casing has a thinner wall portion at said one end of said conductive casing with inward casing flanges at each end of said thinner wall portion, said thinner wall portion holding said main body of said plug and said inward casing flanges holding portions of said outward plug extension and an inner end wall portion of said plug main body.

25. A switch according to claim 17 with said compression spring construction including a relatively strong compression spring between said pelelt and said el'ec trically conductive member and with a relatively weak compression spring between said plug and said pin head.

26. A switch according to claim 25 with said strong compression spring having spring load distributing disc means adjacent one of its ends.

27. A switch according to claim 25 with said strong compression spring having one spring end engaging a spring load distributing disc means adjacent said pellet and with its other spring end engaging said central portion of said conductive member.

28. A switch according to claim 25 with said conductive casing having an integral conductive end wall closure at the other end of said conductive casing, and with said first conductor connected to said conductive end wall closure.

29. A switch according to claim 28 with said pellet being adjacent said integral end wall closure.

30. A switch according to claim 25 with said weak compression spring having spring load distributing disc means in the form of said pin head adjacent one of its ends.

31. A switch comprising: a cylindrical tubular electrically and thermally conductive casing having a closure at each end of said cas'mg; one of said closures being electrically non-conductive; a first conductor conductively contacting said casing; a second conductor extending into said casing through said electrically non-conductive closure; a normally solid fusible pellet spring biased to exert outward pressure against one of said closures; an electrically conductive member slidably mounted within said casing, said member having a resilient peripheral conductive engagement with said conductive casing, and having a conductive central portion in electrical flow condition with said second electrical conductor in one position and out of electrical flow condition with said second electrical conductor in another position; and a compression spring construction outside said pellet held under compression between said member and said casing to change the electric flow condition between said casing and said electrical conductor upon collapse of said pellet; said non-conductive closure including a rigid insulating plug having a plug central opening surrounding said second conductor, said plug being located and secured in said conductive casing and having a large diameter cylindrical main body engaging the inside surface of said conductive casing, said plug having a smaller diameter outwardly tapered plug extension at one plug end extending out of one end of said conductor casing, said tapered extension and casing end being covered with a sealing compound, said second conductor having an arresting conductor head means engaging said plug to hold said second conductor from moving outwardly, and said second conductor extending out said central opening and out of said smaller diameter outward plug extension, and means to maintain said central portion of said electrically conductive member in electrical flow condi tion with said arresting conductor head means in said one position and out of electrical flow condition with said arresting conductor head means in said another position.

32. A switch according to claim 31 in which said rigid insulating plug has a smaller diameter inward plug extension at the other plug end to engage said arresting conductor head means to hold said second conductor from moving outwardly.

33. A switch according to claim 31 in which said rigid insulating plug has a relatively large plug cavity in said 9 10 main body with an opening extending toward the interior 3,291,945 12/ 1966 Merrill et a1. 337403 of said conductor casing and with a cavity lbottom adja- 3,281,559 10/1966 Ebensteiner 33740'3 cent said plug extension and receiving said arresting 3,180,958 4/1965 Merrill 337-409 conductor head means to hold said second conductor from 3,309,481 3/ 1967 Merrill 337407 X moving outwardly.

5 H. B. GILSON, Primary Examiner References Cited U S c1 X R UNITED STATES PATENTS 337 403 2,955,179 10/1960 Milton et a1. 337---403 

